1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor light emitting device whose thermal saturation level and kink level are improved, and more particularly to a method of manufacturing a semiconductor light emitting device having ridges, for example, stripe sections constituting current paths.
2. Description of the Related Art
Hitherto, in the manufacture of semiconductor light emitting devices, for example, semiconductor lasers, grooves of desired shapes have often been formed (for example, see Japanese Patent Application Publication 2003-60307, Paragraph 0030).
Usually, the formation of grooves is performed by anisotropic etching or isotropic etching, as illustrated in, for instance, schematic cross-sectional views of FIGS. 9 and 10.
First, a first conductive type buffer layer 103, a first conductive type cladding layer 104, an active layer 105, a second conductive type (for example, a p-type) first cladding layer 106, a second conductive type etching stop layer 107, a second conductive type second cladding layer, a second conductive type intermediate layer 109, and a second conductive type cap layer 110 are sequentially formed on a first conductive type (for example, an n-type) semiconductor substrate by epitaxial growth through, for example, MOCVD (Metal Organic Chemical Vapor Deposition). Thus, a multi-layered semiconductor layer 111 is formed.
Subsequently, as illustrated in FIG. 9A, a mask layer 112 made of SiO2 serving as an etching mask in the next process is formed on the cap layer 110 of the multi-layered semiconductor layer 111. This mask layer is pattern-etched to thereby form openings 113 in a ridge groove formation section.
Next, as illustrated in FIG. 9B, a ridge groove 114 is formed by wet etching using, for example, a sulfate-based etchant in such a way as to extend across the cap layer 110, the intermediate layer 109, and the second conductive type second cladding layer 108 of the multi-layered semiconductor layer 111 to the etching stop layer 107.
Next, the mask layer 112 is removed. Further, as illustrated in FIG. 10A, first conductive type GaAs buried layers 116 are formed. Then, as illustrated in FIG. 10B, a first electrode 117 is formed in such a way as to thoroughly cover the entire top surfaces of the buried layers 116 and the cap layers 110. A second electrode 118 is formed on the backside of the substrate 102.
Thus, a semiconductor light emitting device 101 is manufactured.
In the manufacture of such a kind of a semiconductor light emitting device, when isotropic etching is performed so as to form the grooves, each of the grooves is shaped in such a way as to be tapered in cross-section plane so that an upper width W1 shown in FIG. 10A is smaller than a lower width W2 shown therein. In the case of ordinary lasers, such a tapered shape of a cross section of each of the grooves presents no problems.